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I agree with Robert. What's the alternative reading people make of
"circle of radius 1cm rolls round the outside a circle of 3cm"? Put a
mark on each and line up the marks, as Point A. Roll the little one
round the big one and it has 1/3 the circumference so has rotated 3
times when the marks align again. Simples.

-----Original Message-----
From: email list for Radical Statistics [mailto:[log in to unmask]]
On Behalf Of Moore, Robert
Sent: 16 June 2011 14:03
To: [log in to unmask]
Subject: Re: Oh those exam questions!

Have I missed something here? I though Jane was correct.

The question is 'how many time does the circumference of one circle go
into the other?'. Circumference is 2 x pi x r
If A is on the larger circle we need to divide larger by smaller
circumference, 2 x pi will be on top and bottom of the division and
cancel out - leaving the answer as 3. (done in your head!)

Or is that too easy?

Robert





Professor Robert Moore
School of Sociology and Social Policy
Eleanor Rathbone Building
The University of Liverpool
L69 7ZA

Telephone and fax: 44 (0) 1352 714456
________________________________________
From: email list for Radical Statistics [[log in to unmask]] On
Behalf Of Ted Harding [[log in to unmask]]
Sent: 16 June 2011 13:17
To: [log in to unmask]
Subject: Re: Oh those exam questions!

On 16-Jun-11 10:15:56, Gavin and Rosemary Ross wrote:
> It was said that in the USA a multiple choice maths question
> was answered by over 100,000 examinees of whom only one had
> the temerity to point out that all the answers were wrong.
> The question was as follows:
> "A circle of radius 1cm rolls round the outside a circle of 3cm.
> The point A is the initial point of contact of the two circles.
> How many revolutions does the smaller circle make before it
> returns to point A?
> 2? 3? 4.5? 6?"

In this case I put it down to an episode of hyperactivity of the
Examiner's Limboid System[*], manifest in this case by failure to
proof-read (in lay terms: not reading the question you have written).
It would have been OK with candidate answers "2? 3? 4? 5? 6?"
[the correct answer is 4].

> A Cambridge statistical examiner was criticised for asking
> candidates to prove that both the sum and the difference of
> two Poisson variables has the Poisson distribution. This time
> the bolder entrants did comment that Poisson variables cannot
> be negative.

I hope that the "Cambridge statistical examiner" was someone
in the Cambridge GCSE Exam Board, and not a Cambridge University
statistical examiner (been there, but I hope I ain't done that).

This one may possibly be due to another Limboid spasm (crossed
wires causing "Normal" to be replaced by "Poisson"). On the other
hand, perhaps more probably, it is the result of a folkloric
belief by the examiner that, in the domain of discrete distribution,
the Poisson has all the nice properties that the Normal has in
the domain of continuous distributions (from which the assertion
in the question follows immediately).

> Gavin Ross

[*] The Limboid System is a Neuropsychology thing which I have
discovered through personal observation. It is not to be confused
with the Limbic System, which is a Neuroanatomy thing. The name
"Limboid" is etymologically derived from the word "Limbo". The
Limboid system is that system of the mind which is responsible for
-- Getting wrong that which needs to be got right
-- Forgetting that which needs to be remembered
-- Overlooking that which needs to be noticed
-- Mistaking one thing for another thing which is totally different
-- Putting off till later that which need to be done now, until
such time as that which needs to be done now is no longer relevant
-- Etc.
[PS: I never got round to writing it up]

Best wishes to all,
Ted.

> ----- Original Message -----
> From: "Ted Harding" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, June 09, 2011 8:22 AM
> Subject: Oh those exam questions!
>
>
>> Greetings All!
>> Perhaps a bit off-topic for us, but I reckon it's a
>> good place to ask the question.
>>
>> I've been repeatedly hearing/seeing teasing news items
>> about the "unanswerable" AS-level exam questions set by
>> different exam boards:
>>
>> A maths question which was impossible to answer
>> because not enough information was given (OCR)
>>
>> A business studies question which did not give enough
>> information (AQA)
>>
>> A multiple-choice biology question which gave several
>> possible answers but not the correct one (Edexcel)
>>
>> (descriptions quoted from the BBC News website).
>>
>> I say "teasing" because I'd love to know the details of
>> these questions, just to see how "goofy" they really are.
>> But nowhere have I come across citations of the actual
>> questions themselves, nor any detail much more specific
>> than the above.
>>
>> So can anyone provide full citations, or pointers to where
>> they can be found?
>>
>> My interest is aroused because I've set (and seen) a good
>> few exam questions in my time, and therefore have an eye
>> for the "warning signs" of a dodgy question. I'd like to
>> be able to see how blatant these were in the above cases!
>>
>> With thanks, and best wishes to all.
>> And apologies if I have set an unanswerable question.
>>
>> Ted.
>>
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